// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_VIEWS_VIEW_H_
#define UI_VIEWS_VIEW_H_

#include <stddef.h>

#include <algorithm>
#include <map>
#include <set>
#include <string>
#include <vector>

#include "base/compiler_specific.h"
#include "base/i18n/rtl.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "build/build_config.h"
#include "ui/accessibility/ax_enums.h"
#include "ui/base/accelerators/accelerator.h"
#include "ui/base/dragdrop/drag_drop_types.h"
#include "ui/base/dragdrop/drop_target_event.h"
#include "ui/base/dragdrop/os_exchange_data.h"
#include "ui/base/ui_base_types.h"
#include "ui/compositor/layer_delegate.h"
#include "ui/compositor/layer_owner.h"
#include "ui/compositor/paint_cache.h"
#include "ui/events/event.h"
#include "ui/events/event_target.h"
#include "ui/gfx/geometry/insets.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/gfx/geometry/vector2d.h"
#include "ui/gfx/native_widget_types.h"
#include "ui/views/view_targeter.h"
#include "ui/views/views_export.h"

#if defined(OS_WIN)
#include "base/win/scoped_comptr.h"
#endif

using ui::OSExchangeData;

namespace gfx {
class Canvas;
class Insets;
class Path;
class Transform;
}

namespace ui {
struct AXViewState;
class Compositor;
class InputMethod;
class Layer;
class NativeTheme;
class PaintContext;
class TextInputClient;
class Texture;
class ThemeProvider;
}

namespace views {

class Background;
class Border;
class ContextMenuController;
class DragController;
class FocusManager;
class FocusTraversable;
class LayoutManager;
class NativeViewAccessibility;
class ScrollView;
class Widget;

namespace internal {
    class PreEventDispatchHandler;
    class PostEventDispatchHandler;
    class RootView;
}

/////////////////////////////////////////////////////////////////////////////
//
// View class
//
//   A View is a rectangle within the views View hierarchy. It is the base
//   class for all Views.
//
//   A View is a container of other Views (there is no such thing as a Leaf
//   View - makes code simpler, reduces type conversion headaches, design
//   mistakes etc)
//
//   The View contains basic properties for sizing (bounds), layout (flex,
//   orientation, etc), painting of children and event dispatch.
//
//   The View also uses a simple Box Layout Manager similar to XUL's
//   SprocketLayout system. Alternative Layout Managers implementing the
//   LayoutManager interface can be used to lay out children if required.
//
//   It is up to the subclass to implement Painting and storage of subclass -
//   specific properties and functionality.
//
//   Unless otherwise documented, views is not thread safe and should only be
//   accessed from the main thread.
//
/////////////////////////////////////////////////////////////////////////////
class VIEWS_EXPORT View : public ui::LayerDelegate,
                          public ui::LayerOwner,
                          public ui::AcceleratorTarget,
                          public ui::EventTarget,
                          public ui::EventHandler {
public:
    typedef std::vector<View*> Views;

    struct ViewHierarchyChangedDetails {
        ViewHierarchyChangedDetails()
            : is_add(false)
            , parent(NULL)
            , child(NULL)
            , move_view(NULL)
        {
        }

        ViewHierarchyChangedDetails(bool is_add,
            View* parent,
            View* child,
            View* move_view)
            : is_add(is_add)
            , parent(parent)
            , child(child)
            , move_view(move_view)
        {
        }

        bool is_add;
        // New parent if |is_add| is true, old parent if |is_add| is false.
        View* parent;
        // The view being added or removed.
        View* child;
        // If this is a move (reparent), meaning AddChildViewAt() is invoked with an
        // existing parent, then a notification for the remove is sent first,
        // followed by one for the add.  This case can be distinguished by a
        // non-NULL |move_view|.
        // For the remove part of move, |move_view| is the new parent of the View
        // being removed.
        // For the add part of move, |move_view| is the old parent of the View being
        // added.
        View* move_view;
    };

    // Creation and lifetime -----------------------------------------------------

    View();
    ~View() override;

    // By default a View is owned by its parent unless specified otherwise here.
    void set_owned_by_client() { owned_by_client_ = true; }

    // Tree operations -----------------------------------------------------------

    // Get the Widget that hosts this View, if any.
    virtual const Widget* GetWidget() const;
    virtual Widget* GetWidget();

    // Adds |view| as a child of this view, optionally at |index|.
    void AddChildView(View* view);
    void AddChildViewAt(View* view, int index);

    // Moves |view| to the specified |index|. A negative value for |index| moves
    // the view at the end.
    void ReorderChildView(View* view, int index);

    // Removes |view| from this view. The view's parent will change to NULL.
    void RemoveChildView(View* view);

    // Removes all the children from this view. If |delete_children| is true,
    // the views are deleted, unless marked as not parent owned.
    void RemoveAllChildViews(bool delete_children);

    int child_count() const { return static_cast<int>(children_.size()); }
    bool has_children() const { return !children_.empty(); }

    // Returns the child view at |index|.
    const View* child_at(int index) const
    {
        DCHECK_GE(index, 0);
        DCHECK_LT(index, child_count());
        return children_[index];
    }
    View* child_at(int index)
    {
        return const_cast<View*>(const_cast<const View*>(this)->child_at(index));
    }

    // Returns the parent view.
    const View* parent() const { return parent_; }
    View* parent() { return parent_; }

    // Returns true if |view| is contained within this View's hierarchy, even as
    // an indirect descendant. Will return true if child is also this view.
    bool Contains(const View* view) const;

    // Returns the index of |view|, or -1 if |view| is not a child of this view.
    int GetIndexOf(const View* view) const;

    // Size and disposition ------------------------------------------------------
    // Methods for obtaining and modifying the position and size of the view.
    // Position is in the coordinate system of the view's parent.
    // Position is NOT flipped for RTL. See "RTL positioning" for RTL-sensitive
    // position accessors.
    // Transformations are not applied on the size/position. For example, if
    // bounds is (0, 0, 100, 100) and it is scaled by 0.5 along the X axis, the
    // width will still be 100 (although when painted, it will be 50x50, painted
    // at location (0, 0)).

    void SetBounds(int x, int y, int width, int height);
    void SetBoundsRect(const gfx::Rect& bounds);
    void SetSize(const gfx::Size& size);
    void SetPosition(const gfx::Point& position);
    void SetX(int x);
    void SetY(int y);

    // No transformation is applied on the size or the locations.
    const gfx::Rect& bounds() const { return bounds_; }
    int x() const { return bounds_.x(); }
    int y() const { return bounds_.y(); }
    int width() const { return bounds_.width(); }
    int height() const { return bounds_.height(); }
    const gfx::Size& size() const { return bounds_.size(); }

    // Returns the bounds of the content area of the view, i.e. the rectangle
    // enclosed by the view's border.
    gfx::Rect GetContentsBounds() const;

    // Returns the bounds of the view in its own coordinates (i.e. position is
    // 0, 0).
    gfx::Rect GetLocalBounds() const;

    // Returns the bounds of the layer in its own pixel coordinates.
    gfx::Rect GetLayerBoundsInPixel() const;

    // Returns the insets of the current border. If there is no border an empty
    // insets is returned.
    virtual gfx::Insets GetInsets() const;

    // Returns the visible bounds of the receiver in the receivers coordinate
    // system.
    //
    // When traversing the View hierarchy in order to compute the bounds, the
    // function takes into account the mirroring setting and transformation for
    // each View and therefore it will return the mirrored and transformed version
    // of the visible bounds if need be.
    gfx::Rect GetVisibleBounds() const;

    // Return the bounds of the View in screen coordinate system.
    gfx::Rect GetBoundsInScreen() const;

    // Returns the baseline of this view, or -1 if this view has no baseline. The
    // return value is relative to the preferred height.
    virtual int GetBaseline() const;

    // Get the size the View would like to be, if enough space were available.
    virtual gfx::Size GetPreferredSize() const;

    // Convenience method that sizes this view to its preferred size.
    void SizeToPreferredSize();

    // Gets the minimum size of the view. View's implementation invokes
    // GetPreferredSize.
    virtual gfx::Size GetMinimumSize() const;

    // Gets the maximum size of the view. Currently only used for sizing shell
    // windows.
    virtual gfx::Size GetMaximumSize() const;

    // Return the height necessary to display this view with the provided width.
    // View's implementation returns the value from getPreferredSize.cy.
    // Override if your View's preferred height depends upon the width (such
    // as with Labels).
    virtual int GetHeightForWidth(int w) const;

    // Sets whether this view is visible. Painting is scheduled as needed. Also,
    // clears focus if the focused view or one of its ancestors is set to be
    // hidden.
    virtual void SetVisible(bool visible);

    // Return whether a view is visible
    bool visible() const { return visible_; }

    // Returns true if this view is drawn on screen.
    virtual bool IsDrawn() const;

    // Set whether this view is enabled. A disabled view does not receive keyboard
    // or mouse inputs. If |enabled| differs from the current value, SchedulePaint
    // is invoked. Also, clears focus if the focused view is disabled.
    void SetEnabled(bool enabled);

    // Returns whether the view is enabled.
    bool enabled() const { return enabled_; }

    // This indicates that the view completely fills its bounds in an opaque
    // color. This doesn't affect compositing but is a hint to the compositor to
    // optimize painting.
    // Note that this method does not implicitly create a layer if one does not
    // already exist for the View, but is a no-op in that case.
    void SetFillsBoundsOpaquely(bool fills_bounds_opaquely);

    // Transformations -----------------------------------------------------------

    // Methods for setting transformations for a view (e.g. rotation, scaling).

    gfx::Transform GetTransform() const;

    // Clipping parameters. Clipping is done relative to the view bounds.
    void set_clip_insets(gfx::Insets clip_insets) { clip_insets_ = clip_insets; }

    // Sets the transform to the supplied transform.
    void SetTransform(const gfx::Transform& transform);

    // Sets whether this view paints to a layer. A view paints to a layer if
    // either of the following are true:
    // . the view has a non-identity transform.
    // . SetPaintToLayer(true) has been invoked.
    // View creates the Layer only when it exists in a Widget with a non-NULL
    // Compositor.
    void SetPaintToLayer(bool paint_to_layer);

    // Overridden from ui::LayerOwner:
    scoped_ptr<ui::Layer> RecreateLayer() override;

    // RTL positioning -----------------------------------------------------------

    // Methods for accessing the bounds and position of the view, relative to its
    // parent. The position returned is mirrored if the parent view is using a RTL
    // layout.
    //
    // NOTE: in the vast majority of the cases, the mirroring implementation is
    //       transparent to the View subclasses and therefore you should use the
    //       bounds() accessor instead.
    gfx::Rect GetMirroredBounds() const;
    gfx::Point GetMirroredPosition() const;
    int GetMirroredX() const;

    // Given a rectangle specified in this View's coordinate system, the function
    // computes the 'left' value for the mirrored rectangle within this View. If
    // the View's UI layout is not right-to-left, then bounds.x() is returned.
    //
    // UI mirroring is transparent to most View subclasses and therefore there is
    // no need to call this routine from anywhere within your subclass
    // implementation.
    int GetMirroredXForRect(const gfx::Rect& rect) const;

    // Given the X coordinate of a point inside the View, this function returns
    // the mirrored X coordinate of the point if the View's UI layout is
    // right-to-left. If the layout is left-to-right, the same X coordinate is
    // returned.
    //
    // Following are a few examples of the values returned by this function for
    // a View with the bounds {0, 0, 100, 100} and a right-to-left layout:
    //
    // GetMirroredXCoordinateInView(0) -> 100
    // GetMirroredXCoordinateInView(20) -> 80
    // GetMirroredXCoordinateInView(99) -> 1
    int GetMirroredXInView(int x) const;

    // Given a X coordinate and a width inside the View, this function returns
    // the mirrored X coordinate if the View's UI layout is right-to-left. If the
    // layout is left-to-right, the same X coordinate is returned.
    //
    // Following are a few examples of the values returned by this function for
    // a View with the bounds {0, 0, 100, 100} and a right-to-left layout:
    //
    // GetMirroredXCoordinateInView(0, 10) -> 90
    // GetMirroredXCoordinateInView(20, 20) -> 60
    int GetMirroredXWithWidthInView(int x, int w) const;

    // Layout --------------------------------------------------------------------

    // Lay out the child Views (set their bounds based on sizing heuristics
    // specific to the current Layout Manager)
    virtual void Layout();

    // TODO(beng): I think we should remove this.
    // Mark this view and all parents to require a relayout. This ensures the
    // next call to Layout() will propagate to this view, even if the bounds of
    // parent views do not change.
    void InvalidateLayout();

    // Gets/Sets the Layout Manager used by this view to size and place its
    // children.
    // The LayoutManager is owned by the View and is deleted when the view is
    // deleted, or when a new LayoutManager is installed.
    LayoutManager* GetLayoutManager() const;
    void SetLayoutManager(LayoutManager* layout);

    // Adjust the layer's offset so that it snaps to the physical pixel boundary.
    // This has no effect if the view does not have an associated layer.
    void SnapLayerToPixelBoundary();

    // Attributes ----------------------------------------------------------------

    // The view class name.
    static const char kViewClassName[];

    // Return the receiving view's class name. A view class is a string which
    // uniquely identifies the view class. It is intended to be used as a way to
    // find out during run time if a view can be safely casted to a specific view
    // subclass. The default implementation returns kViewClassName.
    virtual const char* GetClassName() const;

    // Returns the first ancestor, starting at this, whose class name is |name|.
    // Returns null if no ancestor has the class name |name|.
    const View* GetAncestorWithClassName(const std::string& name) const;
    View* GetAncestorWithClassName(const std::string& name);

    // Recursively descends the view tree starting at this view, and returns
    // the first child that it encounters that has the given ID.
    // Returns NULL if no matching child view is found.
    virtual const View* GetViewByID(int id) const;
    virtual View* GetViewByID(int id);

    // Gets and sets the ID for this view. ID should be unique within the subtree
    // that you intend to search for it. 0 is the default ID for views.
    int id() const { return id_; }
    void set_id(int id) { id_ = id; }

    // A group id is used to tag views which are part of the same logical group.
    // Focus can be moved between views with the same group using the arrow keys.
    // Groups are currently used to implement radio button mutual exclusion.
    // The group id is immutable once it's set.
    void SetGroup(int gid);
    // Returns the group id of the view, or -1 if the id is not set yet.
    int GetGroup() const;

    // If this returns true, the views from the same group can each be focused
    // when moving focus with the Tab/Shift-Tab key.  If this returns false,
    // only the selected view from the group (obtained with
    // GetSelectedViewForGroup()) is focused.
    virtual bool IsGroupFocusTraversable() const;

    // Fills |views| with all the available views which belong to the provided
    // |group|.
    void GetViewsInGroup(int group, Views* views);

    // Returns the View that is currently selected in |group|.
    // The default implementation simply returns the first View found for that
    // group.
    virtual View* GetSelectedViewForGroup(int group);

    // Coordinate conversion -----------------------------------------------------

    // Note that the utility coordinate conversions functions always operate on
    // the mirrored position of the child Views if the parent View uses a
    // right-to-left UI layout.

    // Convert a point from the coordinate system of one View to another.
    //
    // |source| and |target| must be in the same widget, but doesn't need to be in
    // the same view hierarchy.
    // Neither |source| nor |target| can be NULL.
    static void ConvertPointToTarget(const View* source,
        const View* target,
        gfx::Point* point);

    // Convert |rect| from the coordinate system of |source| to the coordinate
    // system of |target|.
    //
    // |source| and |target| must be in the same widget, but doesn't need to be in
    // the same view hierarchy.
    // Neither |source| nor |target| can be NULL.
    static void ConvertRectToTarget(const View* source,
        const View* target,
        gfx::RectF* rect);

    // Convert a point from a View's coordinate system to that of its Widget.
    static void ConvertPointToWidget(const View* src, gfx::Point* point);

    // Convert a point from the coordinate system of a View's Widget to that
    // View's coordinate system.
    static void ConvertPointFromWidget(const View* dest, gfx::Point* p);

    // Convert a point from a View's coordinate system to that of the screen.
    static void ConvertPointToScreen(const View* src, gfx::Point* point);

    // Convert a point from a View's coordinate system to that of the screen.
    static void ConvertPointFromScreen(const View* dst, gfx::Point* point);

    // Applies transformation on the rectangle, which is in the view's coordinate
    // system, to convert it into the parent's coordinate system.
    gfx::Rect ConvertRectToParent(const gfx::Rect& rect) const;

    // Converts a rectangle from this views coordinate system to its widget
    // coordinate system.
    gfx::Rect ConvertRectToWidget(const gfx::Rect& rect) const;

    // Painting ------------------------------------------------------------------

    // Mark all or part of the View's bounds as dirty (needing repaint).
    // |r| is in the View's coordinates.
    // Rectangle |r| should be in the view's coordinate system. The
    // transformations are applied to it to convert it into the parent coordinate
    // system before propagating SchedulePaint up the view hierarchy.
    // TODO(beng): Make protected.
    virtual void SchedulePaint();
    virtual void SchedulePaintInRect(const gfx::Rect& r);

    // Called by the framework to paint a View. Performs translation and clipping
    // for View coordinates and language direction as required, allows the View
    // to paint itself via the various OnPaint*() event handlers and then paints
    // the hierarchy beneath it.
    void Paint(const ui::PaintContext& parent_context);

    // The background object is owned by this object and may be NULL.
    void set_background(Background* b);
    const Background* background() const { return background_.get(); }
    Background* background() { return background_.get(); }

    // The border object is owned by this object and may be NULL.
    virtual void SetBorder(scoped_ptr<Border> b);
    const Border* border() const { return border_.get(); }
    Border* border() { return border_.get(); }

    // Get the theme provider from the parent widget.
    const ui::ThemeProvider* GetThemeProvider() const;

    // Returns the NativeTheme to use for this View. This calls through to
    // GetNativeTheme() on the Widget this View is in, or provides a default
    // theme if there's no widget. Warning: the default theme might not be
    // correct; you should probably override OnNativeThemeChanged().
    ui::NativeTheme* GetNativeTheme()
    {
        return const_cast<ui::NativeTheme*>(
            const_cast<const View*>(this)->GetNativeTheme());
    }
    const ui::NativeTheme* GetNativeTheme() const;

    // RTL painting --------------------------------------------------------------

    // This method determines whether the gfx::Canvas object passed to
    // View::Paint() needs to be transformed such that anything drawn on the
    // canvas object during View::Paint() is flipped horizontally.
    //
    // By default, this function returns false (which is the initial value of
    // |flip_canvas_on_paint_for_rtl_ui_|). View subclasses that need to paint on
    // a flipped gfx::Canvas when the UI layout is right-to-left need to call
    // EnableCanvasFlippingForRTLUI().
    bool FlipCanvasOnPaintForRTLUI() const
    {
        return flip_canvas_on_paint_for_rtl_ui_ ? base::i18n::IsRTL() : false;
    }

    // Enables or disables flipping of the gfx::Canvas during View::Paint().
    // Note that if canvas flipping is enabled, the canvas will be flipped only
    // if the UI layout is right-to-left; that is, the canvas will be flipped
    // only if base::i18n::IsRTL() returns true.
    //
    // Enabling canvas flipping is useful for leaf views that draw an image that
    // needs to be flipped horizontally when the UI layout is right-to-left
    // (views::Button, for example). This method is helpful for such classes
    // because their drawing logic stays the same and they can become agnostic to
    // the UI directionality.
    virtual void EnableCanvasFlippingForRTLUI(bool enable);

    // Input ---------------------------------------------------------------------
    // The points, rects, mouse locations, and touch locations in the following
    // functions are in the view's coordinates, except for a RootView.

    // A convenience function which calls into GetEventHandlerForRect() with
    // a 1x1 rect centered at |point|. |point| is in the local coordinate
    // space of |this|.
    View* GetEventHandlerForPoint(const gfx::Point& point);

    // Returns the View that should be the target of an event having |rect| as
    // its location, or NULL if no such target exists. |rect| is in the local
    // coordinate space of |this|.
    View* GetEventHandlerForRect(const gfx::Rect& rect);

    // Returns the deepest visible descendant that contains the specified point
    // and supports tooltips. If the view does not contain the point, returns
    // NULL.
    virtual View* GetTooltipHandlerForPoint(const gfx::Point& point);

    // Return the cursor that should be used for this view or the default cursor.
    // The event location is in the receiver's coordinate system. The caller is
    // responsible for managing the lifetime of the returned object, though that
    // lifetime may vary from platform to platform. On Windows and Aura,
    // the cursor is a shared resource.
    virtual gfx::NativeCursor GetCursor(const ui::MouseEvent& event);

    // A convenience function which calls HitTestRect() with a rect of size
    // 1x1 and an origin of |point|. |point| is in the local coordinate space
    // of |this|.
    bool HitTestPoint(const gfx::Point& point) const;

    // Returns true if |rect| intersects this view's bounds. |rect| is in the
    // local coordinate space of |this|.
    bool HitTestRect(const gfx::Rect& rect) const;

    // Returns true if this view or any of its descendants are permitted to
    // be the target of an event.
    virtual bool CanProcessEventsWithinSubtree() const;

    // Returns true if the mouse cursor is over |view| and mouse events are
    // enabled.
    bool IsMouseHovered() const;

    // This method is invoked when the user clicks on this view.
    // The provided event is in the receiver's coordinate system.
    //
    // Return true if you processed the event and want to receive subsequent
    // MouseDraggged and MouseReleased events.  This also stops the event from
    // bubbling.  If you return false, the event will bubble through parent
    // views.
    //
    // If you remove yourself from the tree while processing this, event bubbling
    // stops as if you returned true, but you will not receive future events.
    // The return value is ignored in this case.
    //
    // Default implementation returns true if a ContextMenuController has been
    // set, false otherwise. Override as needed.
    //
    virtual bool OnMousePressed(const ui::MouseEvent& event);

    // This method is invoked when the user clicked on this control.
    // and is still moving the mouse with a button pressed.
    // The provided event is in the receiver's coordinate system.
    //
    // Return true if you processed the event and want to receive
    // subsequent MouseDragged and MouseReleased events.
    //
    // Default implementation returns true if a ContextMenuController has been
    // set, false otherwise. Override as needed.
    //
    virtual bool OnMouseDragged(const ui::MouseEvent& event);

    // This method is invoked when the user releases the mouse
    // button. The event is in the receiver's coordinate system.
    //
    // Default implementation notifies the ContextMenuController is appropriate.
    // Subclasses that wish to honor the ContextMenuController should invoke
    // super.
    virtual void OnMouseReleased(const ui::MouseEvent& event);

    // This method is invoked when the mouse press/drag was canceled by a
    // system/user gesture.
    virtual void OnMouseCaptureLost();

    // This method is invoked when the mouse is above this control
    // The event is in the receiver's coordinate system.
    //
    // Default implementation does nothing. Override as needed.
    virtual void OnMouseMoved(const ui::MouseEvent& event);

    // This method is invoked when the mouse enters this control.
    //
    // Default implementation does nothing. Override as needed.
    virtual void OnMouseEntered(const ui::MouseEvent& event);

    // This method is invoked when the mouse exits this control
    // The provided event location is always (0, 0)
    // Default implementation does nothing. Override as needed.
    virtual void OnMouseExited(const ui::MouseEvent& event);

    // Set the MouseHandler for a drag session.
    //
    // A drag session is a stream of mouse events starting
    // with a MousePressed event, followed by several MouseDragged
    // events and finishing with a MouseReleased event.
    //
    // This method should be only invoked while processing a
    // MouseDragged or MousePressed event.
    //
    // All further mouse dragged and mouse up events will be sent
    // the MouseHandler, even if it is reparented to another window.
    //
    // The MouseHandler is automatically cleared when the control
    // comes back from processing the MouseReleased event.
    //
    // Note: if the mouse handler is no longer connected to a
    // view hierarchy, events won't be sent.
    //
    // TODO(sky): rename this.
    virtual void SetMouseHandler(View* new_mouse_handler);

    // Invoked when a key is pressed or released.
    // Subclasser should return true if the event has been processed and false
    // otherwise. If the event has not been processed, the parent will be given a
    // chance.
    virtual bool OnKeyPressed(const ui::KeyEvent& event);
    virtual bool OnKeyReleased(const ui::KeyEvent& event);

    // Invoked when the user uses the mousewheel. Implementors should return true
    // if the event has been processed and false otherwise. This message is sent
    // if the view is focused. If the event has not been processed, the parent
    // will be given a chance.
    virtual bool OnMouseWheel(const ui::MouseWheelEvent& event);

    // See field for description.
    void set_notify_enter_exit_on_child(bool notify)
    {
        notify_enter_exit_on_child_ = notify;
    }
    bool notify_enter_exit_on_child() const
    {
        return notify_enter_exit_on_child_;
    }

    // Convenience method to retrieve the InputMethod associated with the
    // Widget that contains this view.
    ui::InputMethod* GetInputMethod()
    {
        return const_cast<ui::InputMethod*>(
            const_cast<const View*>(this)->GetInputMethod());
    }
    const ui::InputMethod* GetInputMethod() const;

    // Sets a new ViewTargeter for the view, and returns the previous
    // ViewTargeter.
    scoped_ptr<ViewTargeter> SetEventTargeter(scoped_ptr<ViewTargeter> targeter);

    // Returns the ViewTargeter installed on |this| if one exists,
    // otherwise returns the ViewTargeter installed on our root view.
    // The return value is guaranteed to be non-null.
    ViewTargeter* GetEffectiveViewTargeter() const;

    ViewTargeter* targeter() const { return targeter_.get(); }

    // Overridden from ui::EventTarget:
    bool CanAcceptEvent(const ui::Event& event) override;
    ui::EventTarget* GetParentTarget() override;
    scoped_ptr<ui::EventTargetIterator> GetChildIterator() const override;
    ui::EventTargeter* GetEventTargeter() override;
    void ConvertEventToTarget(ui::EventTarget* target,
        ui::LocatedEvent* event) override;

    // Overridden from ui::EventHandler:
    void OnKeyEvent(ui::KeyEvent* event) override;
    void OnMouseEvent(ui::MouseEvent* event) override;
    void OnScrollEvent(ui::ScrollEvent* event) override;
    void OnTouchEvent(ui::TouchEvent* event) final;
    void OnGestureEvent(ui::GestureEvent* event) override;

    // Accelerators --------------------------------------------------------------

    // Sets a keyboard accelerator for that view. When the user presses the
    // accelerator key combination, the AcceleratorPressed method is invoked.
    // Note that you can set multiple accelerators for a view by invoking this
    // method several times. Note also that AcceleratorPressed is invoked only
    // when CanHandleAccelerators() is true.
    virtual void AddAccelerator(const ui::Accelerator& accelerator);

    // Removes the specified accelerator for this view.
    virtual void RemoveAccelerator(const ui::Accelerator& accelerator);

    // Removes all the keyboard accelerators for this view.
    virtual void ResetAccelerators();

    // Overridden from AcceleratorTarget:
    bool AcceleratorPressed(const ui::Accelerator& accelerator) override;

    // Returns whether accelerators are enabled for this view. Accelerators are
    // enabled if the containing widget is visible and the view is enabled() and
    // IsDrawn()
    bool CanHandleAccelerators() const override;

    // Focus ---------------------------------------------------------------------

    // Returns whether this view currently has the focus.
    virtual bool HasFocus() const;

    // Returns the view that should be selected next when pressing Tab.
    View* GetNextFocusableView();
    const View* GetNextFocusableView() const;

    // Returns the view that should be selected next when pressing Shift-Tab.
    View* GetPreviousFocusableView();

    // Sets the component that should be selected next when pressing Tab, and
    // makes the current view the precedent view of the specified one.
    // Note that by default views are linked in the order they have been added to
    // their container. Use this method if you want to modify the order.
    // IMPORTANT NOTE: loops in the focus hierarchy are not supported.
    void SetNextFocusableView(View* view);

    // Sets whether this view is capable of taking focus. It will clear focus if
    // the focused view is set to be non-focusable.
    // Note that this is false by default so that a view used as a container does
    // not get the focus.
    void SetFocusable(bool focusable);

    // Returns true if this view is |focusable_|, |enabled_| and drawn.
    bool IsFocusable() const;

    // Return whether this view is focusable when the user requires full keyboard
    // access, even though it may not be normally focusable.
    bool IsAccessibilityFocusable() const;

    // Set whether this view can be made focusable if the user requires
    // full keyboard access, even though it's not normally focusable. It will
    // clear focus if the focused view is set to be non-focusable.
    // Note that this is false by default.
    void SetAccessibilityFocusable(bool accessibility_focusable);

    // Convenience method to retrieve the FocusManager associated with the
    // Widget that contains this view.  This can return NULL if this view is not
    // part of a view hierarchy with a Widget.
    virtual FocusManager* GetFocusManager();
    virtual const FocusManager* GetFocusManager() const;

    // Request keyboard focus. The receiving view will become the focused view.
    virtual void RequestFocus();

    // Invoked when a view is about to be requested for focus due to the focus
    // traversal. Reverse is this request was generated going backward
    // (Shift-Tab).
    virtual void AboutToRequestFocusFromTabTraversal(bool reverse) { }

    // Invoked when a key is pressed before the key event is processed (and
    // potentially eaten) by the focus manager for tab traversal, accelerators and
    // other focus related actions.
    // The default implementation returns false, ensuring that tab traversal and
    // accelerators processing is performed.
    // Subclasses should return true if they want to process the key event and not
    // have it processed as an accelerator (if any) or as a tab traversal (if the
    // key event is for the TAB key).  In that case, OnKeyPressed will
    // subsequently be invoked for that event.
    virtual bool SkipDefaultKeyEventProcessing(const ui::KeyEvent& event);

    // Subclasses that contain traversable children that are not directly
    // accessible through the children hierarchy should return the associated
    // FocusTraversable for the focus traversal to work properly.
    virtual FocusTraversable* GetFocusTraversable();

    // Subclasses that can act as a "pane" must implement their own
    // FocusTraversable to keep the focus trapped within the pane.
    // If this method returns an object, any view that's a direct or
    // indirect child of this view will always use this FocusTraversable
    // rather than the one from the widget.
    virtual FocusTraversable* GetPaneFocusTraversable();

    // Tooltips ------------------------------------------------------------------

    // Gets the tooltip for this View. If the View does not have a tooltip,
    // return false. If the View does have a tooltip, copy the tooltip into
    // the supplied string and return true.
    // Any time the tooltip text that a View is displaying changes, it must
    // invoke TooltipTextChanged.
    // |p| provides the coordinates of the mouse (relative to this view).
    virtual bool GetTooltipText(const gfx::Point& p,
        base::string16* tooltip) const;

    // Returns the location (relative to this View) for the text on the tooltip
    // to display. If false is returned (the default), the tooltip is placed at
    // a default position.
    virtual bool GetTooltipTextOrigin(const gfx::Point& p, gfx::Point* loc) const;

    // Context menus -------------------------------------------------------------

    // Sets the ContextMenuController. Setting this to non-null makes the View
    // process mouse events.
    ContextMenuController* context_menu_controller()
    {
        return context_menu_controller_;
    }
    void set_context_menu_controller(ContextMenuController* menu_controller)
    {
        context_menu_controller_ = menu_controller;
    }

    // Provides default implementation for context menu handling. The default
    // implementation calls the ShowContextMenu of the current
    // ContextMenuController (if it is not NULL). Overridden in subclassed views
    // to provide right-click menu display triggerd by the keyboard (i.e. for the
    // Chrome toolbar Back and Forward buttons). No source needs to be specified,
    // as it is always equal to the current View.
    virtual void ShowContextMenu(const gfx::Point& p,
        ui::MenuSourceType source_type);

    // On some platforms, we show context menu on mouse press instead of release.
    // This method returns true for those platforms.
    static bool ShouldShowContextMenuOnMousePress();

    // Returns the location, in screen coordinates, to show the context menu at
    // when the context menu is shown from the keyboard. This implementation
    // returns the middle of the visible region of this view.
    //
    // This method is invoked when the context menu is shown by way of the
    // keyboard.
    virtual gfx::Point GetKeyboardContextMenuLocation();

    // Drag and drop -------------------------------------------------------------

    DragController* drag_controller() { return drag_controller_; }
    void set_drag_controller(DragController* drag_controller)
    {
        drag_controller_ = drag_controller;
    }

    // During a drag and drop session when the mouse moves the view under the
    // mouse is queried for the drop types it supports by way of the
    // GetDropFormats methods. If the view returns true and the drag site can
    // provide data in one of the formats, the view is asked if the drop data
    // is required before any other drop events are sent. Once the
    // data is available the view is asked if it supports the drop (by way of
    // the CanDrop method). If a view returns true from CanDrop,
    // OnDragEntered is sent to the view when the mouse first enters the view,
    // as the mouse moves around within the view OnDragUpdated is invoked.
    // If the user releases the mouse over the view and OnDragUpdated returns a
    // valid drop, then OnPerformDrop is invoked. If the mouse moves outside the
    // view or over another view that wants the drag, OnDragExited is invoked.
    //
    // Similar to mouse events, the deepest view under the mouse is first checked
    // if it supports the drop (Drop). If the deepest view under
    // the mouse does not support the drop, the ancestors are walked until one
    // is found that supports the drop.

    // Override and return the set of formats that can be dropped on this view.
    // |formats| is a bitmask of the formats defined bye OSExchangeData::Format.
    // The default implementation returns false, which means the view doesn't
    // support dropping.
    virtual bool GetDropFormats(
        int* formats,
        std::set<ui::Clipboard::FormatType>* format_types);

    // Override and return true if the data must be available before any drop
    // methods should be invoked. The default is false.
    virtual bool AreDropTypesRequired();

    // A view that supports drag and drop must override this and return true if
    // data contains a type that may be dropped on this view.
    virtual bool CanDrop(const OSExchangeData& data);

    // OnDragEntered is invoked when the mouse enters this view during a drag and
    // drop session and CanDrop returns true. This is immediately
    // followed by an invocation of OnDragUpdated, and eventually one of
    // OnDragExited or OnPerformDrop.
    virtual void OnDragEntered(const ui::DropTargetEvent& event);

    // Invoked during a drag and drop session while the mouse is over the view.
    // This should return a bitmask of the DragDropTypes::DragOperation supported
    // based on the location of the event. Return 0 to indicate the drop should
    // not be accepted.
    virtual int OnDragUpdated(const ui::DropTargetEvent& event);

    // Invoked during a drag and drop session when the mouse exits the views, or
    // when the drag session was canceled and the mouse was over the view.
    virtual void OnDragExited();

    // Invoked during a drag and drop session when OnDragUpdated returns a valid
    // operation and the user release the mouse.
    virtual int OnPerformDrop(const ui::DropTargetEvent& event);

    // Invoked from DoDrag after the drag completes. This implementation does
    // nothing, and is intended for subclasses to do cleanup.
    virtual void OnDragDone();

    // Returns true if the mouse was dragged enough to start a drag operation.
    // delta_x and y are the distance the mouse was dragged.
    static bool ExceededDragThreshold(const gfx::Vector2d& delta);

    // Accessibility -------------------------------------------------------------

    // Modifies |state| to reflect the current accessible state of this view.
    virtual void GetAccessibleState(ui::AXViewState* state) { }

    // Returns an instance of the native accessibility interface for this view.
    virtual gfx::NativeViewAccessible GetNativeViewAccessible();

    // Notifies assistive technology that an accessibility event has
    // occurred on this view, such as when the view is focused or when its
    // value changes. Pass true for |send_native_event| except for rare
    // cases where the view is a native control that's already sending a
    // native accessibility event and the duplicate event would cause
    // problems.
    void NotifyAccessibilityEvent(ui::AXEvent event_type,
        bool send_native_event);

    // Scrolling -----------------------------------------------------------------
    // TODO(beng): Figure out if this can live somewhere other than View, i.e.
    //             closer to ScrollView.

    // Scrolls the specified region, in this View's coordinate system, to be
    // visible. View's implementation passes the call onto the parent View (after
    // adjusting the coordinates). It is up to views that only show a portion of
    // the child view, such as Viewport, to override appropriately.
    virtual void ScrollRectToVisible(const gfx::Rect& rect);

    // The following methods are used by ScrollView to determine the amount
    // to scroll relative to the visible bounds of the view. For example, a
    // return value of 10 indicates the scrollview should scroll 10 pixels in
    // the appropriate direction.
    //
    // Each method takes the following parameters:
    //
    // is_horizontal: if true, scrolling is along the horizontal axis, otherwise
    //                the vertical axis.
    // is_positive: if true, scrolling is by a positive amount. Along the
    //              vertical axis scrolling by a positive amount equates to
    //              scrolling down.
    //
    // The return value should always be positive and gives the number of pixels
    // to scroll. ScrollView interprets a return value of 0 (or negative)
    // to scroll by a default amount.
    //
    // See VariableRowHeightScrollHelper and FixedRowHeightScrollHelper for
    // implementations of common cases.
    virtual int GetPageScrollIncrement(ScrollView* scroll_view,
        bool is_horizontal, bool is_positive);
    virtual int GetLineScrollIncrement(ScrollView* scroll_view,
        bool is_horizontal, bool is_positive);

protected:
    // Used to track a drag. RootView passes this into
    // ProcessMousePressed/Dragged.
    struct DragInfo {
        // Sets possible_drag to false and start_x/y to 0. This is invoked by
        // RootView prior to invoke ProcessMousePressed.
        void Reset();

        // Sets possible_drag to true and start_pt to the specified point.
        // This is invoked by the target view if it detects the press may generate
        // a drag.
        void PossibleDrag(const gfx::Point& p);

        // Whether the press may generate a drag.
        bool possible_drag;

        // Coordinates of the mouse press.
        gfx::Point start_pt;
    };

    // Size and disposition ------------------------------------------------------

    // Override to be notified when the bounds of the view have changed.
    virtual void OnBoundsChanged(const gfx::Rect& previous_bounds);

    // Called when the preferred size of a child view changed.  This gives the
    // parent an opportunity to do a fresh layout if that makes sense.
    virtual void ChildPreferredSizeChanged(View* child) { }

    // Called when the visibility of a child view changed.  This gives the parent
    // an opportunity to do a fresh layout if that makes sense.
    virtual void ChildVisibilityChanged(View* child) { }

    // Invalidates the layout and calls ChildPreferredSizeChanged on the parent
    // if there is one. Be sure to call View::PreferredSizeChanged when
    // overriding such that the layout is properly invalidated.
    virtual void PreferredSizeChanged();

    // Override returning true when the view needs to be notified when its visible
    // bounds relative to the root view may have changed. Only used by
    // NativeViewHost.
    virtual bool GetNeedsNotificationWhenVisibleBoundsChange() const;

    // Notification that this View's visible bounds relative to the root view may
    // have changed. The visible bounds are the region of the View not clipped by
    // its ancestors. This is used for clipping NativeViewHost.
    virtual void OnVisibleBoundsChanged();

    // Override to be notified when the enabled state of this View has
    // changed. The default implementation calls SchedulePaint() on this View.
    virtual void OnEnabledChanged();

    bool needs_layout() const { return needs_layout_; }

    // Tree operations -----------------------------------------------------------

    // This method is invoked when the tree changes.
    //
    // When a view is removed, it is invoked for all children and grand
    // children. For each of these views, a notification is sent to the
    // view and all parents.
    //
    // When a view is added, a notification is sent to the view, all its
    // parents, and all its children (and grand children)
    //
    // Default implementation does nothing. Override to perform operations
    // required when a view is added or removed from a view hierarchy
    //
    // Refer to comments in struct |ViewHierarchyChangedDetails| for |details|.
    virtual void ViewHierarchyChanged(const ViewHierarchyChangedDetails& details);

    // When SetVisible() changes the visibility of a view, this method is
    // invoked for that view as well as all the children recursively.
    virtual void VisibilityChanged(View* starting_from, bool is_visible);

    // This method is invoked when the parent NativeView of the widget that the
    // view is attached to has changed and the view hierarchy has not changed.
    // ViewHierarchyChanged() is called when the parent NativeView of the widget
    // that the view is attached to is changed as a result of changing the view
    // hierarchy. Overriding this method is useful for tracking which
    // FocusManager manages this view.
    virtual void NativeViewHierarchyChanged();

    // Painting ------------------------------------------------------------------

    // Responsible for calling Paint() on child Views. Override to control the
    // order child Views are painted.
    virtual void PaintChildren(const ui::PaintContext& context);

    // Override to provide rendering in any part of the View's bounds. Typically
    // this is the "contents" of the view. If you override this method you will
    // have to call the subsequent OnPaint*() methods manually.
    virtual void OnPaint(gfx::Canvas* canvas);

    // Override to paint a background before any content is drawn. Typically this
    // is done if you are satisfied with a default OnPaint handler but wish to
    // supply a different background.
    virtual void OnPaintBackground(gfx::Canvas* canvas);

    // Override to paint a border not specified by SetBorder().
    virtual void OnPaintBorder(gfx::Canvas* canvas);

    // Accelerated painting ------------------------------------------------------

    // Returns the offset from this view to the nearest ancestor with a layer. If
    // |layer_parent| is non-NULL it is set to the nearest ancestor with a layer.
    virtual gfx::Vector2d CalculateOffsetToAncestorWithLayer(
        ui::Layer** layer_parent);

    // Updates the view's layer's parent. Called when a view is added to a view
    // hierarchy, responsible for parenting the view's layer to the enclosing
    // layer in the hierarchy.
    virtual void UpdateParentLayer();

    // If this view has a layer, the layer is reparented to |parent_layer| and its
    // bounds is set based on |point|. If this view does not have a layer, then
    // recurses through all children. This is used when adding a layer to an
    // existing view to make sure all descendants that have layers are parented to
    // the right layer.
    void MoveLayerToParent(ui::Layer* parent_layer, const gfx::Point& point);

    // Called to update the bounds of any child layers within this View's
    // hierarchy when something happens to the hierarchy.
    void UpdateChildLayerBounds(const gfx::Vector2d& offset);

    // Overridden from ui::LayerDelegate:
    void OnPaintLayer(const ui::PaintContext& context) override;
    void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip) override;
    void OnDeviceScaleFactorChanged(float device_scale_factor) override;
    base::Closure PrepareForLayerBoundsChange() override;

    // Finds the layer that this view paints to (it may belong to an ancestor
    // view), then reorders the immediate children of that layer to match the
    // order of the view tree.
    virtual void ReorderLayers();

    // This reorders the immediate children of |*parent_layer| to match the
    // order of the view tree. Child layers which are owned by a view are
    // reordered so that they are below any child layers not owned by a view.
    // Widget::ReorderNativeViews() should be called to reorder any child layers
    // with an associated view. Widget::ReorderNativeViews() may reorder layers
    // below layers owned by a view.
    virtual void ReorderChildLayers(ui::Layer* parent_layer);

    // Input ---------------------------------------------------------------------

    virtual DragInfo* GetDragInfo();

    // Focus ---------------------------------------------------------------------

    // Returns last value passed to SetFocusable(). Use IsFocusable() to determine
    // if a view can take focus right now.
    bool focusable() const { return focusable_; }

    // Override to be notified when focus has changed either to or from this View.
    virtual void OnFocus();
    virtual void OnBlur();

    // Handle view focus/blur events for this view.
    void Focus();
    void Blur();

    // System events -------------------------------------------------------------

    // Called when the UI theme (not the NativeTheme) has changed, overriding
    // allows individual Views to do special cleanup and processing (such as
    // dropping resource caches).  To dispatch a theme changed notification, call
    // Widget::ThemeChanged().
    virtual void OnThemeChanged() { }

    // Called when the locale has changed, overriding allows individual Views to
    // update locale-dependent strings.
    // To dispatch a locale changed notification, call Widget::LocaleChanged().
    virtual void OnLocaleChanged() { }

    // Tooltips ------------------------------------------------------------------

    // Views must invoke this when the tooltip text they are to display changes.
    void TooltipTextChanged();

    // Drag and drop -------------------------------------------------------------

    // These are cover methods that invoke the method of the same name on
    // the DragController. Subclasses may wish to override rather than install
    // a DragController.
    // See DragController for a description of these methods.
    virtual int GetDragOperations(const gfx::Point& press_pt);
    virtual void WriteDragData(const gfx::Point& press_pt, OSExchangeData* data);

    // Returns whether we're in the middle of a drag session that was initiated
    // by us.
    bool InDrag() const;

    // Returns how much the mouse needs to move in one direction to start a
    // drag. These methods cache in a platform-appropriate way. These values are
    // used by the public static method ExceededDragThreshold().
    static int GetHorizontalDragThreshold();
    static int GetVerticalDragThreshold();

    // NativeTheme ---------------------------------------------------------------

    // Invoked when the NativeTheme associated with this View changes.
    virtual void OnNativeThemeChanged(const ui::NativeTheme* theme) { }

    // Debugging -----------------------------------------------------------------

#if !defined(NDEBUG)
    // Returns string containing a graph of the views hierarchy in graphViz DOT
    // language (http://graphviz.org/). Can be called within debugger and save
    // to a file to compile/view.
    // Note: Assumes initial call made with first = true.
    virtual std::string PrintViewGraph(bool first);

    // Some classes may own an object which contains the children to displayed in
    // the views hierarchy. The above function gives the class the flexibility to
    // decide which object should be used to obtain the children, but this
    // function makes the decision explicit.
    std::string DoPrintViewGraph(bool first, View* view_with_children);
#endif

private:
    friend class internal::PreEventDispatchHandler;
    friend class internal::PostEventDispatchHandler;
    friend class internal::RootView;
    friend class FocusManager;
    friend class ViewLayerTest;
    friend class Widget;

    // Painting  -----------------------------------------------------------------

    enum SchedulePaintType {
        // Indicates the size is the same (only the origin changed).
        SCHEDULE_PAINT_SIZE_SAME,

        // Indicates the size changed (and possibly the origin).
        SCHEDULE_PAINT_SIZE_CHANGED
    };

    // Invoked before and after the bounds change to schedule painting the old and
    // new bounds.
    void SchedulePaintBoundsChanged(SchedulePaintType type);

    // Schedules a paint on the parent View if it exists.
    void SchedulePaintOnParent();

    // Tree operations -----------------------------------------------------------

    // Removes |view| from the hierarchy tree.  If |update_focus_cycle| is true,
    // the next and previous focusable views of views pointing to this view are
    // updated.  If |update_tool_tip| is true, the tooltip is updated.  If
    // |delete_removed_view| is true, the view is also deleted (if it is parent
    // owned).  If |new_parent| is not NULL, the remove is the result of
    // AddChildView() to a new parent.  For this case, |new_parent| is the View
    // that |view| is going to be added to after the remove completes.
    void DoRemoveChildView(View* view,
        bool update_focus_cycle,
        bool update_tool_tip,
        bool delete_removed_view,
        View* new_parent);

    // Call ViewHierarchyChanged() for all child views and all parents.
    // |old_parent| is the original parent of the View that was removed.
    // If |new_parent| is not NULL, the View that was removed will be reparented
    // to |new_parent| after the remove operation.
    void PropagateRemoveNotifications(View* old_parent, View* new_parent);

    // Call ViewHierarchyChanged() for all children.
    void PropagateAddNotifications(const ViewHierarchyChangedDetails& details);

    // Propagates NativeViewHierarchyChanged() notification through all the
    // children.
    void PropagateNativeViewHierarchyChanged();

    // Takes care of registering/unregistering accelerators if
    // |register_accelerators| true and calls ViewHierarchyChanged().
    void ViewHierarchyChangedImpl(bool register_accelerators,
        const ViewHierarchyChangedDetails& details);

    // Invokes OnNativeThemeChanged() on this and all descendants.
    void PropagateNativeThemeChanged(const ui::NativeTheme* theme);

    // Size and disposition ------------------------------------------------------

    // Call VisibilityChanged() recursively for all children.
    void PropagateVisibilityNotifications(View* from, bool is_visible);

    // Registers/unregisters accelerators as necessary and calls
    // VisibilityChanged().
    void VisibilityChangedImpl(View* starting_from, bool is_visible);

    // Responsible for propagating bounds change notifications to relevant
    // views.
    void BoundsChanged(const gfx::Rect& previous_bounds);

    // Visible bounds notification registration.
    // When a view is added to a hierarchy, it and all its children are asked if
    // they need to be registered for "visible bounds within root" notifications
    // (see comment on OnVisibleBoundsChanged()). If they do, they are registered
    // with every ancestor between them and the root of the hierarchy.
    static void RegisterChildrenForVisibleBoundsNotification(View* view);
    static void UnregisterChildrenForVisibleBoundsNotification(View* view);
    void RegisterForVisibleBoundsNotification();
    void UnregisterForVisibleBoundsNotification();

    // Adds/removes view to the list of descendants that are notified any time
    // this views location and possibly size are changed.
    void AddDescendantToNotify(View* view);
    void RemoveDescendantToNotify(View* view);

    // Sets the layer's bounds given in DIP coordinates.
    void SetLayerBounds(const gfx::Rect& bounds_in_dip);

    // Transformations -----------------------------------------------------------

    // Returns in |transform| the transform to get from coordinates of |ancestor|
    // to this. Returns true if |ancestor| is found. If |ancestor| is not found,
    // or NULL, |transform| is set to convert from root view coordinates to this.
    bool GetTransformRelativeTo(const View* ancestor,
        gfx::Transform* transform) const;

    // Coordinate conversion -----------------------------------------------------

    // Convert a point in the view's coordinate to an ancestor view's coordinate
    // system using necessary transformations. Returns whether the point was
    // successfully converted to the ancestor's coordinate system.
    bool ConvertPointForAncestor(const View* ancestor, gfx::Point* point) const;

    // Convert a point in the ancestor's coordinate system to the view's
    // coordinate system using necessary transformations. Returns whether the
    // point was successfully converted from the ancestor's coordinate system
    // to the view's coordinate system.
    bool ConvertPointFromAncestor(const View* ancestor, gfx::Point* point) const;

    // Convert a rect in the view's coordinate to an ancestor view's coordinate
    // system using necessary transformations. Returns whether the rect was
    // successfully converted to the ancestor's coordinate system.
    bool ConvertRectForAncestor(const View* ancestor, gfx::RectF* rect) const;

    // Convert a rect in the ancestor's coordinate system to the view's
    // coordinate system using necessary transformations. Returns whether the
    // rect was successfully converted from the ancestor's coordinate system
    // to the view's coordinate system.
    bool ConvertRectFromAncestor(const View* ancestor, gfx::RectF* rect) const;

    // Accelerated painting ------------------------------------------------------

    // Creates the layer and related fields for this view.
    void CreateLayer();

    // Parents all un-parented layers within this view's hierarchy to this view's
    // layer.
    void UpdateParentLayers();

    // Parents this view's layer to |parent_layer|, and sets its bounds and other
    // properties in accordance to |offset|, the view's offset from the
    // |parent_layer|.
    void ReparentLayer(const gfx::Vector2d& offset, ui::Layer* parent_layer);

    // Called to update the layer visibility. The layer will be visible if the
    // View itself, and all its parent Views are visible. This also updates
    // visibility of the child layers.
    void UpdateLayerVisibility();
    void UpdateChildLayerVisibility(bool visible);

    // Orphans the layers in this subtree that are parented to layers outside of
    // this subtree.
    void OrphanLayers();

    // Destroys the layer associated with this view, and reparents any descendants
    // to the destroyed layer's parent.
    void DestroyLayer();

    // Input ---------------------------------------------------------------------

    bool ProcessMousePressed(const ui::MouseEvent& event);
    bool ProcessMouseDragged(const ui::MouseEvent& event);
    void ProcessMouseReleased(const ui::MouseEvent& event);

    // Accelerators --------------------------------------------------------------

    // Registers this view's keyboard accelerators that are not registered to
    // FocusManager yet, if possible.
    void RegisterPendingAccelerators();

    // Unregisters all the keyboard accelerators associated with this view.
    // |leave_data_intact| if true does not remove data from accelerators_ array,
    // so it could be re-registered with other focus manager
    void UnregisterAccelerators(bool leave_data_intact);

    // Focus ---------------------------------------------------------------------

    // Initialize the previous/next focusable views of the specified view relative
    // to the view at the specified index.
    void InitFocusSiblings(View* view, int index);

    // Helper function to advance focus, in case the currently focused view has
    // become unfocusable.
    void AdvanceFocusIfNecessary();

    // System events -------------------------------------------------------------

    // Used to propagate theme changed notifications from the root view to all
    // views in the hierarchy.
    void PropagateThemeChanged();

    // Used to propagate locale changed notifications from the root view to all
    // views in the hierarchy.
    void PropagateLocaleChanged();

    // Used to propagate device scale factor changed notifications from the root
    // view to all views in the hierarchy.
    void PropagateDeviceScaleFactorChanged(float device_scale_factor);

    // Tooltips ------------------------------------------------------------------

    // Propagates UpdateTooltip() to the TooltipManager for the Widget.
    // This must be invoked any time the View hierarchy changes in such a way
    // the view under the mouse differs. For example, if the bounds of a View is
    // changed, this is invoked. Similarly, as Views are added/removed, this
    // is invoked.
    void UpdateTooltip();

    // Drag and drop -------------------------------------------------------------

    // Starts a drag and drop operation originating from this view. This invokes
    // WriteDragData to write the data and GetDragOperations to determine the
    // supported drag operations. When done, OnDragDone is invoked. |press_pt| is
    // in the view's coordinate system.
    // Returns true if a drag was started.
    bool DoDrag(const ui::LocatedEvent& event,
        const gfx::Point& press_pt,
        ui::DragDropTypes::DragEventSource source);

    //////////////////////////////////////////////////////////////////////////////

    // Creation and lifetime -----------------------------------------------------

    // False if this View is owned by its parent - i.e. it will be deleted by its
    // parent during its parents destruction. False is the default.
    bool owned_by_client_;

    // Attributes ----------------------------------------------------------------

    // The id of this View. Used to find this View.
    int id_;

    // The group of this view. Some view subclasses use this id to find other
    // views of the same group. For example radio button uses this information
    // to find other radio buttons.
    int group_;

    // Tree operations -----------------------------------------------------------

    // This view's parent.
    View* parent_;

    // This view's children.
    Views children_;

    // Size and disposition ------------------------------------------------------

    // This View's bounds in the parent coordinate system.
    gfx::Rect bounds_;

    // Whether this view is visible.
    bool visible_;

    // Whether this view is enabled.
    bool enabled_;

    // When this flag is on, a View receives a mouse-enter and mouse-leave event
    // even if a descendant View is the event-recipient for the real mouse
    // events. When this flag is turned on, and mouse moves from outside of the
    // view into a child view, both the child view and this view receives
    // mouse-enter event. Similarly, if the mouse moves from inside a child view
    // and out of this view, then both views receive a mouse-leave event.
    // When this flag is turned off, if the mouse moves from inside this view into
    // a child view, then this view receives a mouse-leave event. When this flag
    // is turned on, it does not receive the mouse-leave event in this case.
    // When the mouse moves from inside the child view out of the child view but
    // still into this view, this view receives a mouse-enter event if this flag
    // is turned off, but doesn't if this flag is turned on.
    // This flag is initialized to false.
    bool notify_enter_exit_on_child_;

    // Whether or not RegisterViewForVisibleBoundsNotification on the RootView
    // has been invoked.
    bool registered_for_visible_bounds_notification_;

    // List of descendants wanting notification when their visible bounds change.
    scoped_ptr<Views> descendants_to_notify_;

    // Transformations -----------------------------------------------------------

    // Clipping parameters. skia transformation matrix does not give us clipping.
    // So we do it ourselves.
    gfx::Insets clip_insets_;

    // Layout --------------------------------------------------------------------

    // Whether the view needs to be laid out.
    bool needs_layout_;

    // The View's LayoutManager defines the sizing heuristics applied to child
    // Views. The default is absolute positioning according to bounds_.
    scoped_ptr<LayoutManager> layout_manager_;

    // Whether this View's layer should be snapped to the pixel boundary.
    bool snap_layer_to_pixel_boundary_;

    // Painting ------------------------------------------------------------------

    // Background
    scoped_ptr<Background> background_;

    // Border.
    scoped_ptr<Border> border_;

    // Cached output of painting to be reused in future frames until invalidated.
    ui::PaintCache paint_cache_;

    // RTL painting --------------------------------------------------------------

    // Indicates whether or not the gfx::Canvas object passed to View::Paint()
    // is going to be flipped horizontally (using the appropriate transform) on
    // right-to-left locales for this View.
    bool flip_canvas_on_paint_for_rtl_ui_;

    // Accelerated painting ------------------------------------------------------

    bool paint_to_layer_;

    // Accelerators --------------------------------------------------------------

    // Focus manager accelerators registered on.
    FocusManager* accelerator_focus_manager_;

    // The list of accelerators. List elements in the range
    // [0, registered_accelerator_count_) are already registered to FocusManager,
    // and the rest are not yet.
    scoped_ptr<std::vector<ui::Accelerator>> accelerators_;
    size_t registered_accelerator_count_;

    // Focus ---------------------------------------------------------------------

    // Next view to be focused when the Tab key is pressed.
    View* next_focusable_view_;

    // Next view to be focused when the Shift-Tab key combination is pressed.
    View* previous_focusable_view_;

    // Whether this view can be focused.
    bool focusable_;

    // Whether this view is focusable if the user requires full keyboard access,
    // even though it may not be normally focusable.
    bool accessibility_focusable_;

    // Context menus -------------------------------------------------------------

    // The menu controller.
    ContextMenuController* context_menu_controller_;

    // Drag and drop -------------------------------------------------------------

    DragController* drag_controller_;

    // Input  --------------------------------------------------------------------

    scoped_ptr<ViewTargeter> targeter_;

    // Accessibility -------------------------------------------------------------

    // Belongs to this view, but it's reference-counted on some platforms
    // so we can't use a scoped_ptr. It's dereferenced in the destructor.
    NativeViewAccessibility* native_view_accessibility_;

    DISALLOW_COPY_AND_ASSIGN(View);
};

} // namespace views

#endif // UI_VIEWS_VIEW_H_
